A multiple input multiple output (MIMO) wireless communications system may obtain diversity and array gains by using a transmit precoding technology and a receive signal combination technology. A system using precoding may be indicated asy=H{circumflex over (V)}s+n 
where y is a vector of a received signal, H is a channel matrix, {circumflex over (V)} is a precoding matrix, s is a vector of a transmitted symbol, and n is a measured noise.
Optimal precoding generally requires that a transmitter completely knows channel state information (CSI). A frequently used method is that user equipment (UE) quantizes instantaneous CSI and reports the quantized instantaneous CSI to a base station, where the user equipment includes a mobile station (MS), a relay (Relay), a mobile telephone (Mobile Telephone), a handset (handset), portable equipment (portable equipment) and the like, and the base station includes a node B (NodeB) base station (BS), an access point (Access Point), a transmission point (TP), an evolved node B (eNB), a relay (Relay) or the like. CSI information reported by an existing Long Term Evolution (LTE) system includes information about a rank indicator (RI), information about a precoding matrix indicator (PMI), information about a channel quality indicator (CQI), and the like, where the RI and the PMI respectively indicate a quantity of transmission layers and a precoding matrix that are used. A set of precoding matrices in use is generally referred to as a codebook, and each of the precoding matrices is a codeword in the codebook.
Codebook design used in existing LTE systems is all based on inter-antenna strong related features. However, as a spacing between two antennas in the same polarization direction increases, an inter-antenna correlation gradually decreases, while phase differences between antenna elements involved in a codebook based on inter-antenna strong related features all keep consistent. Therefore, when the existing codebook design is applied to a scenario in which a large spacing is configured between antennas, good matching cannot be achieved, which results in that the precision at which a base station performs precoding according to PMI information fed back by UE is reduced, thereby causing a large performance loss, and reducing the system throughput.